I have tried all sorts of combinations, even with cider vinegar. The problem is, too much liquid makes the mayonnaise too runny, and more or stronger mustard or vinegar changes the flavor.

I have since tried adding a little citric acid powder which definitely gives more zest to the mayonnaise.

I think one would have to be very cautious as to the amount used, since it is obviously very concentrated and using too much could have health implications - I believe some people are sensitive to citric acid.

I am still experimenting with this idea and just wondered if anyone else had gone this route.

Re the thinness caused by too much liquid, have you tried using less oil? This video shows making mayo with only 1/2 cup vs. the traditional 3/4 cup of oil (for one egg) and it turns out thicker mayo:
http://www.youtube.com/watch?v=MMAliJ9DlR0
I bookmarked video that because I'd like to reduce the amount of oil anyway, and the thicker mayo (without even refrigerating) appealed to me too, though haven't actually tried it yet.

Did you also try using powdered mustard or fairly "dry' ground, to decrease the liquid if you weren't already doing that?
And have you tried white vinegar too (which should be stronger in tartness than any of the flavored vinegars)?
(Btw, I think most recipes use a bit more acid than you are with just 2 teaspoons.)

". . .Water
The oil droplets have to be suspended in an aqueous medium—water. About half of the water in a classic yolk-based mayonnaise comes from the egg yolk, while the rest comes from the vinegar. In whole-egg mayonnaise, additional water is provided by the egg white. If you’re feeling creative, substitute freshly squeezed lemon or lime juice or any other juice or flavoured liquid for the vinegar.
To make yolk-based mayonnaise, be sure there is at least 15 ml (1 tablespoon) of liquid for every 250 ml (1 cup) of oil. Otherwise the oil droplets will be packed too tightly, leaving your mayonnaise at risk of separating and developing an oily consistency (see table, p. 15).
If you want to add extra liquid to achieve a more distinctive flavour, it’s best to add it to finished mayonnaise."

I made some mayo with an inversion blender recently (it came out fine) and I tried it again just yesterday, but it failed twice. I had read that u can't do it during a thunderstorm, but didn't believe it. apparantly due to the electrical charge in the air, you can't emulsify during a storm. I am surprised that no one has mentioned this here. I wasn't even able to save it the next day. Did anyone else have the same problem?

Also, if you like hellmanns or best foods mayo, you can check out top secret recipes for their version.

Interesting...hadn't heard that. It does seem to show up here and there online and in some old books, etc, suggesting the cause is either excess humidity or something to do with the "positive and negative charges" at those times.

If the air is somewhat more highly ionized than normal, if there are reactions going on in the mayo (proto-mayo?) that involve ion exchange, you certainly can have an impact on the process...
Todd K. Pedlar

I agree. Protein emulsion is dependent on the negative charge of certain amide groups that are chemically reduced. A heavily charge atmosphere can really mess it up.
I used to run into a similar problem in experiments with protein on colloids (basically, I was analyzing what happened to manure in soil, if you really want to know). The emulsions sometimes wouldn't form if there was a big thunderstorm out.
R. Victor Bottomly

This was one of the first sites I found when first exploring how to make mayo. Since then, however, after some years of making it my food processor, I discovered immersion blender mayo. It's much, much quicker and much easier to clean up after.

Process: put the egg followed by everything else in a tall, narrow vessel, insert stick blender, turn it on, and voila! In 10 seconds or less you've got mayonnaise. Usually, that is.

After several foolproof (I thought) makings, suddenly I had a batch that didn't emulsify. Today, for about the third time, I again had a batch that didn't emulsify. I had to use another egg, get it blending, and then slowly add the unmulsified mixture to the new egg before I could make mayo and salvage the bad batch.

Surely there is some scientific answer for why some batches fail to emulsify while others do it immediately. Anyone got a clue?

-1 egg(whole, with the white, 2 eggs for more mayo),
-lemon juice(or i use citric acid, the one that looks like sugar, as a substitute - vinegar gives it weird taste),
-salt(NaCl)
-oil(sunflower one, haven't tried with olive, but it should work).

I use blender for the job, after i found that it's very hard to curdle the oil and the egg together by hand(after 40 mins of hand pain...).
So, i put the egg(yolk and white), salt and lemon juice in deep jam-jar(works best for me) and mix them. Then i start to drip the oil and use the blender, so they can curdle. After i get the desired density, it's finished.
IMPORTANT: You HAVE to pour the oil slowly and by little in the mixture, otherwise it will not curdle and you'll get a jar of oil and egg - not the mayo. If you put all the oil and then start to blend it - nothing will happen. Found that after i wasted a bottle of oil

I haven't specified any exact proportions for the ingredients, because everyone have different taste. Salt and lemon juice depend on how salty and sourly you like it, oil depends on the density you want - more oil makes it denser.
TIPS:
-If you get the mayo more dense, sour or saltier, you can add a bit water and blend it more.
-If the mixture doesn't curdle, you can put another egg in second empty jar and try again, but this time using the content of the first jar instead of oil - again slowly pouring it into the second jar(otherwise you'll just waste the content of the first jar. You probably will need to add more oil to get the desired density - resulting more mayo, but you'll not waste the mix).

Contrary to the recipe and all the comments here saying that immediate refrigeration is absolutely necessary for safety, the opposite is true.

NUMEROUS scientific studies have investigated the question of sterilization of homemade mayonnaise. If you happen to have one of those 1 in 30,000 infected eggs (and it is not pasteurized), the only way to sterilize your mayonnaise is by using a sufficient amount of acid AND leaving it out at room temperature for 24-72 hours.

1. Put the first 6 ingredients into a narrow cylindrical container (Mine is 7cm x 14cm)
2. Stir for a few seconds
3. Add the intact egg yolk carefully to the mixture
4. Top up slowly with the oil
5. Place the blender with the whisk attachment over the egg yolk
6. Using the highest speed, switch on. After a few seconds, mayonnaise will start to form under the blade housing
7. Keeping the blender on, slowly lift the machine up at a slight angle – you will see the oil being absorbed and turned into mayonnaise. Do not raise the blender out of the mixture. Move the blender up and down a few times if necessary.
This process takes 15 – 20 seconds
8. Voila! - delicious mayo.